curl --request PUT \
  --url https://api.meetcampfire.com/rr/api/v1/contracts/{contract_id}/subscriptions/{id} \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '{
  "is_contract_amendment": true,
  "start_date": "2023-12-25",
  "end_date": "2023-12-25",
  "mrr": 0,
  "notes": "<string>",
  "use_daily_accounting": true,
  "use_catchup": true,
  "catchup_date": "2023-12-25",
  "contract": 123,
  "product": 123,
  "modified_subscription": 123
}'

{
  "id": 123,
  "lines": "<string>",
  "product_name": "<string>",
  "total_value": 0,
  "is_contract_amendment": true,
  "start_date": "2023-12-25",
  "end_date": "2023-12-25",
  "mrr": 0,
  "notes": "<string>",
  "use_daily_accounting": true,
  "use_catchup": true,
  "catchup_date": "2023-12-25",
  "created_at": "2023-11-07T05:31:56Z",
  "last_modified_at": "2023-11-07T05:31:56Z",
  "customer": 123,
  "contract": 123,
  "product": 123,
  "modified_subscription": 123
}